Low-molecular-weight peptides from deer antler velvet: Antioxidant potential, biosafety, and synergistic interaction with nanomelanin.

Deer antler velvet (DAV) is a precious pharmaceutical source. Low-molecular-weight peptides (LMWPs) extracted from DAV have been reported as promising pharmaceutical ingredients with various potential applications across different health care areas. Components, molecular weights, and bioactivities of DAV's peptides may vary depending on the production protocols. This study optimised an enzyme-based protocol for DAV protein digestion to obtain DAV peptides (as LMWPs form) and investigated bioactivities of the LMWPs. Different enzymes as single forms and/or combined forms were applied for digestion of DAV to create DAV peptides. Then, DAV peptides were mapped by proteomics analysis using LC/MS system. It indicated that sequential treatment with pepsin and trypsin yielded a distinct pool of LMWPs of below 10 kDa. Moreover, 8288 LMWPs from 1405 DAV's proteins digested by combined pepsin and trypsin were mapped. This LMWPs sample exhibited strong antioxidant activity in the ABTS assay, with an antioxidant potential of 1 mg/mL, corresponding to that of 1.7 mg/mL Ascorbic acid. Interestingly, the mixture of LMWPs and nano-melanin exhibited synergistic antioxidant effects, resulting in a ~2-fold increase in relative antioxidant potential. In addition, LMWPs at concentrations ranging from 5 to 1000 µg/mL exhibited very low toxicity toward STO cells, and toward zebrafish embryos, with NOEC and LOEC values estimated at 193 mg/L and 289 mg/L, respectively. This study suggests an enzymatic method to digest DAV's proteins to extract bioactive LMWPs, and implies possible combinations of the DAV's LMWPs and nano-melanin to develop nutritional foods and/or pharmaceutical preparations for antioxidant applications.